export function invokeWxPay (payParams) {
  return new Promise((resolve, reject) => {
    const onBridgeReady = () => {
      window.WeixinJSBridge.invoke('getBrandWCPayRequest', {
        appId: payParams.appId,
        timeStamp: payParams.timeStamp,
        nonceStr: payParams.nonceStr,
        package: payParams.package,
        signType: payParams.signType || 'MD5',
        paySign: payParams.paySign
      }, (res) => {
        if (res.err_msg === 'get_brand_wcpay_request:ok') resolve(res)
        else reject(res)
      })
    }
    if (typeof window.WeixinJSBridge === 'undefined') {
      document.addEventListener('WeixinJSBridgeReady', onBridgeReady, false)
    } else {
      onBridgeReady()
    }
  })
}